A carbonate ester is a compound useful as a synthetic raw material for aromatic polycarbonates and pharmaceuticals and agricultural chemicals. A known process for producing a carbonate ester is one that carries out a synthesis by a gas phase reaction using carbon monoxide and nitrite ester in the presence of a platinum group metal solid catalyst (see, for example, Patent Literatures 1 and 2). In such a process, a carbonate ester can be obtained by the following reaction formula (i).CO+2RONO→ROC(═O)OR+2NO  (i)
In the production methods of Patent Literatures 1 and 2, an intended compound is produced by a catalytic reaction while recycling alkyl nitrite as a raw material. In such a production method, a target compound can be produced in large amounts by scaling up but there is a demand for establishment of a technical procedure for the stable continuous production. This is because once the continuous production is interrupted, cumbersome operations such as starting up and shutting down the apparatus are needed and additionally the opportunity loss caused by the operation shutdown increases.
Thus, Patent Literature 2 proposes a technical procedure for preventing the catalytic activity reduction by detecting a concentration of nitrogen monoxide in a supplied gas and adjusting an amount of the molecular oxygen to be supplied based on the obtained concentration. Patent Literature 3 proposes a technical procedure for maintaining the catalytic activity by supplying hydrogen chloride to compensate the chlorine content released from the chloride of the platinum group metal (see, e.g., Patent Literature 3).